1. Field of the Invention
This invention relates generally to telecommunications, and, more particularly, to wireless communications.
2. Description of the Related Art
In the field of wireless telecommunications, such as cellular telephony, a system typically includes a plurality of base stations distributed within an area to be serviced by the system. Various users within the area, fixed or mobile, may then access the system and, thus, other interconnected telecommunications systems, via one or more of the base stations. Typically, a mobile device maintains communications with the system as the mobile device passes through an area by communicating with one and then another base station, as the user moves. The mobile device 120 may communicate with the closest base station, the base station with the strongest signal, the base station with a capacity sufficient to accept communications, etc.
In some wireless systems, communications between the base stations and the mobile devices occur via a radio frequency (RF) system that uses dynamic Time Division Multiple Access (TDMA) to support multiple users via scheduling. That is, each of the multiple users is scheduled to transmit within a specified time slot. TDMA achieves high RF efficiency for general packet data services; however, when Voice over Internet Protocol (VoIP) service is introduced, it degrades the RF efficiency due to its small packet size, which often leads to a poor transport packing efficiency. Further, TDMA has a tight delay budget that also inhibits the RF system from exploiting multi-user diversity gain on the dynamic air interface.
One mechanism that has been employed to improve the VoIP transport efficiency is the use of header compression from source to destination. However, header compression does not address the issue of RF transport efficiency directly. For example, many wireless protocols employ physical framing structure with fixed time duration. Thus, even if the VoIP traffic is header compressed end-to-end, the transport efficiency over an air interface can still be rather poor.
On the RF side, a relatively new high-speed technology commonly referred to as Evolution Data Only (EVDO) attempts to alleviate the issue. EVDO (Rev. A) incorporates a capability of transmitting forward link packets addressed to multiple access terminals in a common time slot, which opens the door to improve the RF efficiency for VoIP transport. However, EVDO has some notable shortcomings. RF scheduler schemes employed in EVDO are not designed to optimize the RF efficiency in a mixed VoIP and data environment. For example, it has been shown the current EVDO Quality of Service (QoS) scheduler suffers a significance loss of RF efficiency once VoIP service is introduced into the system.
The present invention is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.